Millions of dollars in television and online advertisements by an offshoot of the powerful American Israel Political Action Committee are aimed at more than a dozen states represented by undecided Democratic, among them Sens. Joe Manchin of West Virginia, Chris Coons of Delaware and Mark Warner of Virginia. The accord would curb Iran's nuclear program in exchange for relief from economic sanctions, and the House and Senate are slated to vote next month on a resolution of disapproval.

"Iran has violated 20 international agreements and is the leading state sponsor of terrorism," says the ad by Citizens for a Nuclear Free Iran, the AIPAC-sponsored group. "Congress should reject a bad deal. We need a better deal."

As political ads go, experts agree, the commercial is pretty tame. It makes a generic appeal. It doesn't ask viewers to take any action like calling their senator or congressman. And it doesn't name names. Instead, it displays the group's website address, where those inclined to visit will find more information and get automated assistance in calling their lawmaker.

"If part of what you're trying to do is influence members of Congress to vote against the deal - it's not the members of Congress who are going to see this, you're targeting it to their constituents - so I don't understand why there isn't a call to action at the end of the ad. You know, `Call Congress, call your congressman' to generate heat that way," said Rodell Mollineau of Rokk Solutions, who has orchestrated ad campaigns for American Bridge 21st Century, a Democratic super PAC.

But a GOP strategist says a harder-hitting approach would turn off the very Democratic voters the group would like to lobby their lawmakers.

"This looks like an ad aimed at Democratic and independent voters, to get them to contact their senators," said Charlie Black, a veteran of several GOP presidential campaigns. "A low-key, fact-based approach makes sense. The lead says change the deal, in order to refute the claim that the only alternative to the deal is war."

So do lawmakers feel like the ads are tightening the screws? It is August, after all, when fewer eyeballs watch TV and many people are on vacation.

"Sen. Coons is paying closer attention to the calls, emails and letters the office is receiving from constituents regarding the Iran deal," said spokesman Sean Coit.

It's not lost on observers in both parties that AIPAC and its donor base tilts toward Democrats, and many Democratic lawmakers are already upset that they've been cast as anti-Israel and were summoned for a stern lecture by Israel's President Benjamin Netanyahu in a joint meeting of Congress in March. A tougher approach from the group could have backfired and damaged relationships that the group has long nurtured.

A group called Vets Against the Deal has produced a much tougher ad featuring an Iraq War veteran who was badly wounded by a blast from an Iranian-made bomb.

"Every politician who is involved in this will be held accountable. They will have blood on their hands," says retired Staff Sgt. Robert Bartlett, whose facial scars are evident.

The ad was aimed at Sen. Jon Tester, D-Mont., but it's not clear how large a media buy the group is making. The ad won lots of attention from conservative websites and Bartlett appeared on Fox News.

It didn't sway Tester, who announced on Thursday that he was backing the deal. "It's clear this deal is the only option right now to stop Iran from developing a nuclear weapon," the senator said in a statement.

Another group, United Against Nuclear Iran, is also running ads. It's headed by former Sen. Joe Lieberman, I-Conn., though he was enlisted after the group's president, Gary Samore, stepped down because he supports the accord. Also in support is liberal advocacy group J Street, which is spending $5 million to back the agreement.

Meanwhile, 20 Senate Democrats have said they'll vote to preserve the agreement, more than halfway toward the 34 they'll need to sustain a veto. More than 40 House Democrats have come out for it, with 10 against.